276 REPORT — 1901. 



In the actual experiment the solution was slowly evapoi-ated at l^o"*. 

 The deposit was frequently examined with the microscope. At first only 

 Potassium sulphate crystallised out, but subsequently this was mixed with 

 Schonite. As soon as the separation of Potassium chloride was observed 

 to take place the deposited salts were removed and analysed. The 

 amounts found were : — 



25 gms. K2SO4 

 120 gms. K2Mg(S04)2.6H20. 



The amount of the two salts that should be deposited from such a solu- 

 tion may be calculated as follows : — 



At the origin the solution has the composition 



K2S04 + MgCl2 + aH20, 

 from which is deposited 



a;KoS04 +2/.K2Mg(S04)2.6H20, 



whilst 10 parts of solution of the composition represented at M remain— i.e,, 



M)(1000HoO + 25K2CI2 + 21MgCl2 + llMgSO^). 

 Thus 



K2S04 + MgCl2 + aHoO=xK,S04+2/K Mg(S04).,.6H20 

 + «'(1000H2O + 25K2Cl2 + 21MgCl2 + llMgSO4). 



Collecting and equating the coefficients of the various radicles, the 

 values of x, y, and w are determined. 



Thus 



7 7 



The K2SO4 deposited is thus -- of the molecule, i.e., = - x 174-3 



st:26-5 gms. ; whilst the Schonite is ^ of the molecule, i.e., — x 422-8 



= 122-6 gms., which values agree closely with those found by experiment. 

 In following the course of change with the aid of the model, it is 

 noticeable that although, as a rule, concentration proceeds along an 

 upward slope, this is not invariably the case. Thus, whereas on passing 

 from B to F, and from f to G, the slope is upwards, from c to o the slope 

 is downwards ; a slight confusion is thereby introduced. It is to be 

 expected that as concentration proceeds the proportion of molecules of 

 dissolved salt to water molecules should steadily increase ; and as the 

 vertical ordinates represent the number of dissolved molecules, it would 

 seem that the number of molecules in the saturated solution of Magne.sium 

 sulphate is greater than in the solution saturated with Magnesium 

 sulphate and Schonite. If, however, it be assumed that at c a larger pro- 

 portion of the Magnesium sulphate molecules are present in the form 



